The present application is based on and claims priority to Japanese Patent Application No. 11-148459, filed May 27, 1999, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to fuel injector mounting arrangements for direct injection engines. More particularly, the present invention relates to an improved injector mounting arrangement for use in such engines.
2. Related Art
Fuel injected engines come in a variety of types. For instance, in some fuel injected engines, the fuel injector is positioned within the intake passage to provide an air fuel mixture upstream of a combustion chamber. In other arrangements, a fuel injector may be mounted just outside of an intake valve and directed toward a combustion chamber such that the spray of fuel passes through the intake valve and mixes with the air within the combustion chamber. In other arrangements, the injector is positioned to inject fuel directly into a combustion chamber for mixing with air drawn in through an induction system. In such arrangements, the injector is subjected to high temperatures as well as thermal cycling.
In these direct injection engines, gases created during the combustion process sometimes leak around the fuel injectors mounted in the cylinder head. In addition, the flames created during the ignition of the air-fuel charge within the combustion chamber also force themselves within gaps formed within the mounting arrangement of a fuel injector. The migration of the flame, as well as the thermal conductivity of the materials used to mount the fuel injector and the fuel injector itself, can create a number of problems for proper operation of the fuel injector. For instance, a portion of the fuel injector proximate the tip of the fuel injector can become extremely heated, leading to the deposition of carbon deposits about the fuel injector. The formation of the carbon deposits often prohibits the smooth flow of fuel over time. As a result, the total amount of fuel being injected by the injector decreases, leading to rough idling and hesitation during acceleration. This problem is more common in two cycle engines or other types of engines that are run at high speeds and high temperatures.
With reference now to FIG. 1, an earlier fuel injector mounting arrangement is illustrated therein. In this illustrated arrangement, a fuel injector 10 includes a fuel injection nozzle 12 that extends through a portion of a cylinder head 14. The cylinder head 14 partially encloses a combustion chamber 16 into which the fuel passing through the fuel injector 10 is injected. As illustrated, the nozzle 12 extends through an opening 16 in the cylinder head 14 that is directly exposed to flames F that are propagated during the combustion of the air-fuel mixture within the combustion chamber 16. As illustrated in FIG. 1, a gap is defined between the side surface of the nozzle 12 and the opening 18. Therefore, flames directly impinge upon portions of the fuel injector nozzle 12 and increase the temperature of the nozzle 12.
A seal 20 is disposed between the nozzle 12 and a stopping surface 22 of the injector 10. In addition, the seal 20 seats against a lower surface which forms a seat 24 for the seal 20 on the cylinder head 14. The illustrated seal 20 has been curved, which creates a slight gap between its innermost end 26 and the nozzle 12. Thus, the nozzle is further exposed to flames that pass within the gap defined between the nozzle 12 and the cylinder head 14. Moreover, the seal 20 typically is constructed of metal. Therefore, its thermal conductivity is high.
Because the intense heat within the combustion chamber 16 is transmitted to the fuel injector 10, the temperature of the nozzle 12 often has a high temperature as well. Accordingly, heavy substances or components of the fuel are deposited and accumulate around the tip of the fuel injector 10. More particularly, the fuel injector 10 includes a needle valve 28 that controls the flow of fuel through the injector 10. Moreover, the fuel injector 10 includes a swirler 30 as well as a valve seat 32. When the needle valve 28 is seated on the valve seat 32, fuel does not flow through the injector. However, when the needle valve 28 is withdrawn from the valve seat 32, fuel is allowed to flow past the swirler 30 through an injection port 34. When the temperature of the injector nozzle 12 is increased, deposits D typically form about the injection port 34. These deposits inhibit the smooth flow of fuel through the injector port 34 when the needle valve 28 is retracted from the valve seat 32. In addition, under extreme circumstances, the deposits D can form up through the injector port 34 onto a portion of the valve seat 32 such that the needle valve 28 does not properly seat against the valve seat 32, leading to a slow trickle of fuel that can cause dieseling during engine shut-down.
Accordingly, an improved injector mounting arrangement is desired. Preferably, the mounting arrangement reduces the propagation of flames along the sides of the nozzle 12 of the fuel injector 10. In addition, the mounting arrangement preferably seals the sides of the injector nozzle from both combustion gas propagation as well as flame propagation. Moreover, in some arrangements, the seals preferably thermally insulate at least a portion of the injector from the heat being generated within the combustion chamber.
Accordingly, one aspect of the present invention involves a sealing ring for a fuel injector mounting arrangement in which a fuel injector is mounted for direct injection into a combustion chamber. The ring comprises a first layer of heat insulating material and a second outer layer of a thermally activatable material.
Another aspect of the present invention involves a direct injected engine comprising a cylinder, a cylinder head being mounted to said cylinder and a piston being disposed within said cylinder. A combustion chamber is defined at least in part by said piston, said cylinder and said cylinder head. A mounting bore extends through said cylinder head with a fuel injector depending through said mounting bore. The mounting bore includes a stepped seat surface. The fuel injector comprises a nozzle extending between a tip and a seating surface. The nozzle comprises a fuel injection port that is disposed at the tip to inject fuel directly into said combustion chamber. At least one sealing ring is disposed between said about said fuel injector between said seating surface and said seat surface. The sealing ring comprises a thermal insulating component and has a smaller outer diameter than an outer diameter of said seat surface.
A further aspect of the present invention involves a method of sealing a fuel injector within a cylinder head. The method comprises placing at least one sealing ring into a mounting bore of said cylinder head, positioning a fuel injector through said sealing ring, applying a compressive force to secure said fuel injector in position within said mounting bore, and heating said cylinder head to melt a component of said ring.